Charged particle beam system, method of operating a charged particle beam system, method of recording a plurality of images and computer programs for executing the methods

ABSTRACT

The present invention relates to a charged particle beam system comprising a deflection subsystem configured to deflect a charged particle beam in a deflection direction based on a sum of analog signals generated by separate digital to analog conversion of a first digital signal and a second digital signal. The present invention further relates to a method of configuring the charged particle beam system so that each of a plurality of regions of interest can be scanned by varying only the first digital signal while the second digital signal is held constant at a value associated with the respective region of interest. The present invention further relates to a method of recording a plurality of images of the regions of interest at the premise of reduced interference due to charge accumulation.

TECHNICAL FIELD

The present invention relates to a charged particle beam system and amethod of operating a charged particle beam system. In particular thepresent invention relates to a deflection system for deflecting acharged particle beam, a method of configuring the deflection system andusing the charged particle beam system to record a plurality of imagesof remote regions of interest; and a computer program configuring acontroller of a charged particle beam system to execute the method.

Further, the present invention relates to a method of recording aplurality of images of different regions of interest; and a computerprogram configuring a controller of a charged particle beam system toexecute the method.

BACKGROUND

A conventional charged particle beam system comprises a charged particlebeam source configured to generate a charged particle beam, an objectivelens configured to focus the charged particle beam into a focal plane,and a deflection system configured to deflect the charged particle beam.The conventional deflection system comprises a counter, a DAC(digital-to-analog converter), an analog amplifier and a fieldgenerator. The counter generates a digital output value incremented at acontrolled rate. The DAC converts the digital output value output by thecounter into an analog signal. The analog amplifier amplifies the analogsignal output by the DAC and applies the amplified analog signal to thefield generator. The field generator uses the amplified analog signal togenerate a magnetic and/or electric field for deflecting the chargedparticle beam.

A field of application of a charged particle beam system is inspectionof wafers. Wafers are large compared to the field of view of the chargedparticle beam system limited by the deflection system. In order to imageremote regions of interest on the wafer, the field of view of thecharged particle beam system must be large and/or a stage holding thewafer must be moved. According to the conventional deflection system,under the assumption of constant bit depth for the DAC, a large field offield can be configured by selecting a large amplification at the costof reduced spatial sampling frequency of the resulting image becausefield of view and maximum spatial sampling frequency are inverselyinterrelated for a constant bit depth of the DAC. Moving the stagegenerally slows down the acquisition rate of images and introduceserrors due to stage drift. Therefore, the conventional charged particlebeam system lacks capability of imaging remote regions of interest athigh spatial sampling frequency and high accuracy.

Another commonly known problem of recording of images using a chargedparticle beam system is charge accumulation in the sample due toimpinging charged particles of the charged particle beam. This problemcan be severe for samples having low electric conductivity. The chargeaccumulation can generate an unpredictable electric field which affectsthe impinging charged particle beam, resulting in beam deflection andbeam shift and generally in a worse image.

SUMMARY

A feature of the present invention is to provide a charged particle beamsystem and a method of operating a charged particle beam system forimaging remote regions of interest at high spatial sampling frequencyand high accuracy.

The feature is achieved by the subject matter of the independent claims.Preferred embodiments are defined in the dependent claims.

According to a first aspect of the present invention, a charged particlebeam system comprises a charged particle beam source configured togenerate a charged particle beam; an objective lens configured to focusthe charged particle beam into a focal plane; a deflection systemconfigured to deflect the charged particle beam; and a controller. Thedeflection system comprises at least one deflection subsystem. Eachdeflection subsystem is configured to deflect the charged particle beamalong a deflection direction. Multiple deflection subsystems areconfigured to deflect the charged particle beam along differentdeflection directions. Each deflection direction is generallyessentially perpendicular to an optical axis of the charged particlebeam system.

Each deflection subsystem comprises a first DAC circuit configured toconvert a first digital deflection signal into a first analog outputsignal within a first operating range at steps of a first step height, asecond DAC circuit configured to convert a second digital deflectionsignal into a second analog output signal within a second operatingrange at steps of a second step height, a summer configured to receivethe first analog output signal and the second analog output signal andto output an analog deflection signal based on the sum of the receivedfirst analog output signal and the received second analog output signal,and a field generator configured to receive the analog deflection signaland to generate a magnetic and/or electric field for deflecting thecharged particle beam using the received analog deflection signal.

The controller is configured to generate the first digital deflectionsignal and the second digital deflection signal separately for eachdeflection subsystem.

A sample can be located in the focal plane of the objective lens forobserving, analyzing or manipulating the sample.

According to a second aspect of the present invention, a method ofoperating the charged particle beam system comprises: obtainingcoordinates of a plurality of regions of interest on a sample;configuring the first DAC circuit so that a first scanning rangeprovided by the first DAC circuit is at least as large as the largest ofthe regions of interest, the first scanning range representing a lengthof a region in a focal plane of the objective lens scannable by varyingthe first digital deflection signal while maintaining the second digitaldeflection signal; configuring the second DAC circuit so that a secondscanning range provided by the second DAC circuit is at least as largeas the largest distance between the regions of interest, the secondscanning range representing a length of a region in the focal planescannable by varying the second digital deflection signal whilemaintaining the first digital deflection signal; and recording images ofthe regions of interest using the configurations made.

The two DAC circuits of each deflection subsystem can be configured andset individually, for example so that the first DAC circuit provides ahighly accurate small contribution to the analog deflection signalwhereas the second DAC circuit provides a moderately accurate largecontribution to the analog deflection signal. This configuration allowsfor accurate scanning at high spatial sampling frequency (i.e., adjacentdwell locations of the charged particle beam on the sample are close toeach other) within a scanning range provided by the first DAC circuitand for a large field of view provided by a scanning range provided bythe second DAC circuit.

A third aspect of the present invention relates to a method of recordinga plurality of images representing different regions of interest of asample. The method comprises recording a plurality of imagesrepresenting a plurality of different regions of interest on a sample.The recording of the plurality of images comprises scanning a chargedparticle beam over a plurality of scan regions, wherein each of theregions of interest comprises a plurality of the scan regions, whereineach two scan regions to be scanned in succession are separated by atleast a first minimum distance amounting to at least 100 nm, and whereineach two scan regions to be scanned in succession belong to differentones of the regions of interest.

According to this method, each of the images is recorded by recording aplurality of segments of the respective image one after another. Each ofthe segments corresponds to one scan region. Between consecutiverecordings of two segments of a same image by scanning the chargedparticle beam over the scan regions corresponding to the two segments, asegment of another image is recorded by scanning the charged particlebeam over a scan region corresponding to that segment. That is, therecording of two different segments of the same image is interlaced bythe recording of a segment of another image.

In order to reduce the effects of charge accumulation due to thescanning of the charged particle beam over the sample, each two scanregions to be scanned in succession are separated by at least a firstminimum distance amounting to at least 100 nm. Therefore, chargeaccumulated at a first scan region due to the scanning of the chargedparticle beam over the first scan region has little effect on thescanning of a second scan region to be scanned in succession to thefirst scan region, because the second scan region is far away from thefirst scan region. During the scanning of the second scan region, thecharge accumulated at the first scan region can distribute in the sampleor be dissipated. Therefore, a third scan region to be scanned insuccession to the second scan region can be located in proximity of thefirst scan region, and the scanning of the first scan region has littleeffect on the scanning of the third scan region because the chargeaccumulated at the first scan region is distributed or dissipated atthat time.

Therefore, the method allows to record, using a charged particle beam, aplurality of images with reduced interference of charge accumulationcaused by directing the charged particle beam to the sample.

A fourth aspect of the invention relates to a computer programcomprising instructions which, when executed by a controller of acharged particle beam system, enable the charged particle beam system toexecute any of the methods described herein. The methods describedherein can be performed using the charged particle beam systemsdescribed herein.

BRIEF DESCRIPTION OF DRAWINGS

Hereinafter, embodiments of the invention are described with referenceto the accompanying drawings.

FIG. 1 schematically illustrates a charged particle beam systemaccording to an embodiment of the first aspect of the invention.

FIG. 2 schematically illustrates a deflection system of the chargedparticle beam system.

FIG. 3 schematically illustrates digital-to-analog conversions of DACcircuits of the deflection subsystem.

FIG. 4 schematically illustrates scanning ranges provided by the DACcircuits of the deflection subsystem.

FIG. 5 is a flowchart illustrating an embodiment of the second aspect ofthe invention.

FIG. 6 illustrates scan regions on a sample and a scan order of scanningthe scan regions according to an embodiment of the third aspect of theinvention.

FIG. 7 illustrates details regarding the scan regions on the sample.

FIG. 8 illustrates details regarding the regions of interest on thesample.

FIG. 9 is a flowchart illustrating another embodiment of the thirdaspect of the invention.

DETAILED DESCRIPTION

Referring to FIG. 1 , a charged particle beam system 1 according to thefirst aspect of the invention is described. The charged particle beamsystem 1 comprises a charged particle beam column 10, a controller 20and a user interface 30. The user interface 30 is used to configure thecontroller 20. The controller 20 is configured to control the chargedparticle beam column 10. The charged particle beam system 1 can be anelectron beam microscope, for example.

The charged particle beam column 10 comprises a charged particle beamsource 11, an objective lens 12 and a deflection system 13. Depending onthe type of the charged particle beam system, the charged particle beamcolumn 10 can comprise further elements such as condensers, stigmators,detectors and the like. However, for simplicities' sake, such furtherelements are neither illustrated nor described in more detail.

The charged particle beam source 11 is configured to generate a chargedparticle beam 2. The charged particle beam 2 can be a beam of electronsor ions, for example. The charged particle beam source 11 is controlledby the controller 20 as indicated by a connection line 14.

The objective lens 12 is configured to focus the charged particle beam 2onto a focal plane 6. In the present example, a sample 3 is positionedin the focal plane 6. The objective lens 12 can be a magnetic lenscomprising coils configured to generate a magnetic field for focusingthe charged particle beam 2. The objective lens 12 can be an electriclens comprising electrodes configured to generate an electric field forfocusing the charged particle beam 2. The objective lens 12 iscontrolled by the controller 20 as indicated by a connection line 15.

The deflection system 13 is configured to deflect the charged particlebeam 2 in at least one deflection direction. Deflecting the chargedparticle beam 2 means changing the propagation direction of the chargedparticle beam 2. The deflection system 13 is described in more detailwith reference to FIG. 2 .

The charged particle beam system 1 further comprises a stage 4configured to position and orientate the sample 3. The stage 4 iscontrolled by the controller 20 as indicated by a connection line 16.

The charged particle beam system 1 further comprises a vacuum chamber 5accommodating the stage 4 and the sample 3 when held by the stage 4. Thecharged particle beam column 10 is connected to the vacuum chamber 5 sothat the charged particle beam 2 is incident onto the sample 3 held onthe stage 4.

The controller 20 is configured to control the charged particle beamcolumn 10, in particular its components, and the stage 4. The controller20 is connected to the user interface 30 by a connection line 17.

The user interface 30 can be used to define and manipulate parametersused by the controller 20 for controlling. For example, the userinterface 30 can comprise an input device 31 (such as a mouse orkeyboard) for receiving inputs of a user, a processing unit 32 forprocessing the received inputs, and an output device 33 (such as adisplay) for outputting information to the user. The processing unit 32is connected to the controller 20 by the connection line 17. Theprocessing unit 32 can transmit data to the controller 20 forconfiguring the controller 20 and can receive data from the controller20 (such as measurement data, configuration data, etc.).

The deflection system 13 is configured to deflect the charged particlebeam 2 so that the charged particle beam 2 can be directed to aplurality of different locations in the focal plane 6, thereby directingthe charged particle beam 2 to a plurality of different locations on asurface of the sample 3. Directing the charged particle beam 2 to aplurality of different locations in the focal plane 6 by deflecting thecharged particle beam 2 can also be referred to as scanning.

Referring to FIG. 2 , the deflection system 13 is described in moredetail. The deflection system 13 comprises at least one deflectionsubsystem. In the example illustrated in FIG. 2 , the deflection system13 comprises two deflection subsystems 40 and 50. The deflectionsubsystem 40 is configured to deflect the charged particle beam 2 alonga first deflection direction; the deflection subsystem 50 is configuredto deflect the charged particle beam 2 along a second deflectiondirection. The first deflection direction and the second deflectiondirection are different directions which are essentially perpendicularto an optical axis of the charged particle beam system 1 (for example,an optical axis of the objective lens 12). The deflection subsystems 40and 50 have the same principal configuration, but can be set andcontrolled individually.

The deflection subsystem 40 comprises a first DAC circuit 41 configuredto convert a first digital deflection signal 40D1 into a first analogoutput signal 40A1 within a first operating range OR1 at steps of afirst step height SH1. The first operating range OR1 represents a rangeof the first analog output signal 40A1 generatable (i.e., that can begenerated) by the first DAC circuit 41 using a predefined setting. Thefirst step height SH1 represents the smallest difference between firstanalog output signals 40A1 generatable (i.e., that can be generated) bythe first DAC circuit 41 using the predefined setting. Details of thedigital-to-analog conversion of the first DAC circuit 41 are describedwith reference to FIG. 3 .

The deflection subsystem 40 further comprises a second DAC circuit 42configured to convert a second digital deflection signal 40D2 into asecond analog output signal 40A2 within a second operating range OR2 atsteps of a second step height SH2. The second operating range OR2represents a range of the second analog output signal 40A2 generatableby the second DAC circuit 42 using a predefined setting. The second stepheight SH2 represents the smallest difference between second analogoutput signals 40A2 generatable by the second DAC circuit 42 using thepredefined setting. Details of the digital-to-analog conversion of thesecond DAC circuit 42 are described with reference to FIG. 3 .

The first operating range OR1 and the second operating range OR2 aregenerally different from each other. The first step height SH1 and thesecond step height SH2 are generally different from each other.

The deflection subsystem 40 further comprises a summer 43 configured toreceive the first analog output signal 40A1 and the second analog outputsignal 40A2 and to output an analog deflection signal 40A based on thesum of the received first analog output signal 40A1 and the receivedsecond analog output signal 40A2. For example, the summer can be asumming amplifier. The summer can also be referred to as an adder. Forexample, the summer 43 calculates the sum of the received first analogoutput signal 40A1 and the received second analog output signal 40A2 andoutputs the calculated sum as the analog deflection signal 40A.Alternatively, the calculated sum can be amplified by an additionalamplifier, and the amplified calculated sum can be output as the analogdeflection signal 40A.

The deflection subsystem 40 further comprises a field generator 44configured to receive the analog deflection signal 40A and to generate amagnetic and/or electric field for deflecting the charged particle beam2 using the received analog deflection signal 40A. The field generator44 can comprise a coil configured to generate a magnetic field apt todeflect the charged particle beam 2. The field generator 44 can compriseelectrodes configured to generate an electric field apt to deflect thecharged particle beam 2. The received analog deflection signal 40A isused to energize the field generator 44.

The controller 20 determines the first digital deflection signal 40D1and the second digital deflection signal 40D2 and inputs the firstdigital deflection signal 40D1 into the first DAC circuit 41 and inputsthe second digital deflection signal 40D2 into the second DAC circuit42.

In particular, as illustrated in FIG. 2 , the first DAC circuit 41 cancomprise a first DAC 45 configured to convert the first digitaldeflection signal 40D1 into a first analog intermediate signal 40I1 anda first amplifier 46 configured to generate the first analog outputsignal 40A1 by amplifying the first analog intermediate signal 40I1 witha first amplification. Similarly, the second DAC circuit 42 can comprisea second DAC 47 configured to convert the second digital deflectionsignal 40D2 into a second analog intermediate signal 40I2 and a secondamplifier 48 configured to generate the second analog output signal 40A2by amplifying the second analog intermediate signal 40I2 with a secondamplification. The predefined setting of the first DAC circuit 41 can bedefined by a bit depth of the first DAC 45 and the first amplification.The predefined setting of the second DAC circuit 42 can be defined by abit depth of the second DAC 47 and the second amplification. In general,the bit depths and the amplifications can be different from each other.More details of the functionality of the first DAC circuit 41 and thesecond DAC circuit 42 are described with reference to FIG. 3 .

FIG. 3 illustrates a diagram representing a digital-to-analog conversionbehavior of the first DAC circuit 41 and the second DAC circuit 42. Thehorizontal axis of the diagram represents a digital input value inputtedto the first DAC circuit 41 (i.e., potential values of the first digitaldeflection signal 40D1) and a digital input value inputted to the secondDAC circuit 42 (i.e., potential values of the second digital deflectionsignal 40D2). In the present example, it is assumed that the first DACcircuit 41 (the first DAC 45) has a bit depth of n and that the secondDAC circuit 42 (the second DAC 47) has a bit depth of m, wherein m and nare integers and n is greater than m. However, alternatively, the bitdepths m and n can also be the same or m can be greater than n. The bitdepth of a DAC circuit (a DAC) defines the number of bits of the digitalinput value which is converted into an analog output signal by the DACcircuit (the DAC). In this case, the first DAC circuit 41 (the first DAC45) and the second DAC circuit 42 (the second DAC 47) have different bitdepths. However, this is merely an example and the first DAC circuit 41(the first DAC 45) and the second DAC circuit 42 (the second DAC 47) canhave the same bit depth. For saving costs, the second DAC circuit 42(the second DAC 47) can have a lower bit depth than the first DACcircuit 41 (the first DAC 45). For example, the first DAC circuit 41(the first DAC 45) can have a bit depth of 12; and the second DACcircuit 42 (the second DAC 47) can have a bit depth of 8.

The vertical axis of the diagram represents an analog output signalgenerated based on the digital input value. In particular, the firstanalog output signal 40A1 generated by the first DAC circuit 41 isillustrated using circular points; and the second analog output signal40A2 generated by the second DAC circuit 42 is illustrated using diamondpoints. Although not distinguishably illustrated in FIG. 3 , an input ofzero is converted to an output of zero by both the first DAC circuit 41and the second DAC circuit 42.

The first step height SH1 represents the smallest difference betweenfirst analog output signals 40A1 generatable by the first DAC circuit41. I.e., the first step height SH1 represents the difference betweenthe first analog output signals 40A1 generated by the first DAC circuit41 based on a digital input value and that value incremented by 1. Inparticular, the first step height SH1 can be set by the firstamplification of the first amplifier 46.

The second step height SH2 represents the smallest difference betweensecond analog output signals 40A2 generatable by the second DAC circuit42. I.e., the second step height SH2 represents the difference betweenthe second analog output signals 40A2 generated by the second DACcircuit 42 based on a digital input value and that value incrementedby 1. In particular, the second step height SH2 can be set by the secondamplification of the second amplifier 48.

The first operating range OR1 represents a range of the first analogoutput signal 40A1 generatable by the first DAC circuit 41. I.e., thefirst operating range OR1 is the difference between the first analogoutput signals 40A1 generated by the first DAC circuit 41 based on thelargest digital input value (2^(n)−1) and the smallest digital inputvalue (0). In particular, the first operating range OR1 is defined bythe bit depth of the first DAC 45 (n) and the first amplification of thefirst amplifier 46.

The second operating range OR2 represents a range of the second analogoutput signal 40A2 generatable by the second DAC circuit 42. I.e., thesecond operating range OR2 is the difference between the second analogoutput signals 40A2 generated by the second DAC circuit 42 based on thelargest digital input value (2^(m)−1) and the smallest digital inputvalue (0). In particular, the second operating range OR2 is defined bythe bit depth of the second DAC 47 (m) and the second amplification ofthe second amplifier 48.

An accuracy of converting the first digital deflection signal 40D1 intothe first analog output signal 40A1 achieved by the first DAC circuit 41can be defined based on a difference between a real first analog outputsignal 40A1 and an ideal first analog output signal, wherein the betteraccuracy is obtained by the smaller difference. For example, an idealbehavior of the first DAC circuit 41 could be to output idealequidistant steps as an output signal. However, in practice, the realbehavior of the first DAC circuit 41 shows a deviation from the idealbehavior resulting in approximately equidistant steps as the outputsignal.

An accuracy of converting the second digital deflection signal 40D2 intothe second analog output signal 40A2 achieved by the second DAC circuit42 can be defined based on a difference between a real second analogoutput signal 40A2 and an ideal second analog output signal, wherein thebetter accuracy is obtained by the smaller difference. For example, anideal behavior of the second DAC circuit 42 could be to output idealequidistant steps as an output signal. However, in practice, the realbehavior of the second DAC circuit 42 shows a deviation from the idealbehavior resulting in approximately equidistant steps as the outputsignal.

The accuracy of converting the first digital deflection signal 40D1 intothe first analog output signal 40A1 achieved by the first DAC circuit 41can be greater than the accuracy of converting the second digitaldeflection signal 40D2 into the second analog output signal 40A2achieved by the second DAC circuit 42. That is, requirements regardingthe accuracy of the second DAC circuit 42 can be less strict thanrequirements regarding the accuracy of the first DAC circuit 41.

An accuracy of converting the first digital deflection signal 40D1 intothe first analog intermediate signal 40I1 achieved by the first DAC 45can be defined based on a difference between a real first analogintermediate signal 40I1 and an ideal first analog intermediate signal,wherein the better accuracy is obtained by the smaller difference. Forexample, an ideal behavior of the first DAC 45 could be to output idealequidistant steps as an output signal. However, in practice, the realbehavior of the first DAC 45 shows a deviation from the ideal behaviorresulting in approximately equidistant steps as the output signal.

An accuracy of converting the second digital deflection signal 40D2 intothe second analog intermediate signal 40I2 achieved by the second DAC 47can be defined based on a difference between a real second analogintermediate signal 40I2 and an ideal second analog intermediate signal,wherein the better accuracy is obtained by the smaller difference. Forexample, an ideal behavior of the second DAC 47 could be to output idealequidistant steps as an output signal. However, in practice, the realbehavior of the second DAC 47 shows a deviation from the ideal behaviorresulting in approximately equidistant steps as the output signal.

The accuracy of converting the first digital deflection signal 40D1 intothe first analog intermediate signal 40I1 achieved by the first DAC 45can be greater than the accuracy of converting the second digitaldeflection signal 40D2 into the second analog intermediate signal 40I2achieved by the second DAC 47. That is, requirements regarding theaccuracy of the second DAC 47 can be less strict than requirementsregarding the accuracy of the first DAC 45.

The first DAC circuit 41 and the second DAC circuit 42 both contributeto the analog output signal 40A provided to the field generator 44 andthe resulting deflection of the charged particle beam 2. As illustratedin FIG. 3 , the first DAC circuit 41 and the second DAC circuit 42 canbe configured and set so that the contribution of the first analogoutput signal 40A1 to the analog output signal 40A is small but precisewhereas the contribution of the second analog output signal 40A2 to theanalog output signal 40A is large and not necessarily as precise as thatof the first analog output signal 40A1. Such a configuration can beobtained by configuring the first DAC circuit 41 to have a high bitdepth (e.g., 12 bits) and by setting the first amplification smallerthan the second amplification.

As illustrated in FIG. 3 , the first DAC circuit 41 and the second DACcircuit 42 can be configured and set so that the first operating rangeOR1 is approximately equal to the second step height SH2. In particular,the first amplification and the second amplification can be selected sothat the first operating range OR1 is approximately equal to the secondstep height SH2. Other settings are possible. For example, the first DACcircuit 41 and the second DAC circuit 42 can be configured and set sothat the first operating range OR1 is at least half of the second stepheight SH2.

According to another example, the first DAC circuit 41 and the secondDAC circuit 42 can be configured and set so that a ratio of the secondoperating range OR2 to the first operating range OR1 amounts to at least10, in particular at least 100, more in particular at least 200. Inparticular, the first amplification and the second amplification can beselected so that the ratio of the second operating range OR2 to thefirst operating range OR1 amounts to at least 10, in particular at least100, more in particular at least 200.

The advantage of such a configuration and setting is that the first DACcircuit 41 can be used to generate a high precision component of theanalog output signal 40A which is used to record high resolution imagesat high precision while a low precision component of the analog outputsignal 40A generated by the second DAC circuit 42 is maintained (i.e.,kept constant). On the other hand, a large field of view is obtainedfrom the low precision component of the analog output signal 40Agenerated by the second DAC circuit 42.

Referring to FIG. 4 , the contributions of the first analog outputsignal 40A1 and the second analog output signal 40A2 to the analogoutput signal 40A are related to their respective contributions to thedeflecting of the charged particle beam 2. FIG. 4 illustrates the sample3 having a plurality of regions of interest (ROIs) 61, 62. The ROIs 61,62 are located on the surface of the sample 3. The surface of the sample3 is located in the focal plane 6. The ROIs 61, 62 are remote, i.e., theROIs 61, 62 are separated by a distance d which is large compared to afirst scanning range SR1 provided by the first DAC circuit 41.

The first scanning range SR1 represents a length of a region in a focalplane 6 of the objective lens 12 scannable by varying the first digitaldeflection signal 40D1 while maintaining the second digital deflectionsignal 40D2. That is, the first scanning range SR1 represents the lengthof the region (in the focal plane 6 of the objective lens 12) onto whichthe charged particle beam 2 can be directed by deflecting the chargedparticle beam 2 by varying the first digital deflection signal 40D1while not changing the second digital deflection signal 40D2.

Similarly, a second scanning range SR2 represents a length of a regionin the focal plane 6 of the objective lens 12 scannable by varying thesecond digital deflection signal 40D2 while maintaining the firstdigital deflection signal 40D1. That is, the second scanning range SR2represents the length of the region (in the focal plane 6 of theobjective lens 12) onto which the charged particle beam 2 can bedirected by deflecting the charged particle beam 2 by varying the seconddigital deflection signal 40D2 while not changing the first digitaldeflection signal 40D1.

A scanning region (x;0) indicated by a double arrow in FIG. 4 is aregion in the focal plane 6 of the objective lens 12. The first value inthe brackets represents the specific value of the first digitaldeflection signal 40D1; and the second value in the brackets representsthe specific value of the second digital deflection signal 40D2. Thecharged particle beam 2 can be directed to locations of the scanningregion (x;0) by varying the first digital deflection signal 40D1(represented by the variable x ranging from 0 to n−1, where n is the bitdepth of the first DAC circuit 41) while maintaining the second digitaldeflection signal 40D2 at a value of 0 (represented by the specificvalue 0). The length of the scanning region (x;0) represents the firstscanning range SR1 provided by the first DAC circuit 41 (for thespecific value of the second digital deflection signal 40D2 of 0).

Similarly, a scanning region (x;1) indicated by a double arrow in FIG. 4is a region in the focal plane 6 of the objective lens 12. The chargedparticle beam 2 can be directed to locations of the scanning region(x;1) by varying the first digital deflection signal 40D1 (representedby the variable x ranging from 0 to n−1, where n is the bit depth of thefirst DAC circuit 41) while maintaining the second digital deflectionsignal 40D2 at a value of 1 (represented by the specific value 1). Thelength of the scanning region (x;1) represents the first scanning rangeSR1 provided by the first DAC circuit 41 (for the specific value of thesecond digital deflection signal 40D2 of 1).

Similarly, a scanning region (x;2) indicated by a double arrow in FIG. 4is a region in the focal plane 6 of the objective lens 12. The chargedparticle beam 2 can be directed to locations of the scanning region(x;2) by varying the first digital deflection signal 40D1 (representedby the variable x ranging from 0 to n−1, where n is the bit depth of thefirst DAC circuit 41) while maintaining the second digital deflectionsignal 40D2 at a value of 2 (represented by the specific value 2). Thelength of the scanning region (x;2) represents the first scanning rangeSR1 provided by the first DAC circuit 41 (for the specific value of thesecond digital deflection signal 40D2 of 2).

A charged particle beam trajectory indicated (0;m−1) is used toillustrate the scanning range SR2 provided by the second DAC circuit 42,where the specific value of the second digital deflection signal 40D2 ofm−1 indicates the largest possible input value for the second digitaldeflection signal 40D2 based on a bit depth of m for the second DACcircuit 42.

FIG. 5 illustrates a method according to an embodiment of the secondaspect of the invention. The method relates to operating theabove-described charged particle beam system 1. In particular, themethod relates to advantageously configuring the deflection subsystem 40for the sample 3 having remote ROIs 61, 62 as illustrated in FIG. 4 .

In step S1, coordinates of the ROIs 61, 62 on the sample 3 are obtained.The coordinates can represent locations of boundaries of the ROIs 61,62, thereby allowing determination of properties of the ROIs 61, 62 suchas their sizes and shapes. Coordinate data representing the coordinatesof the ROIs 61, 62 can be obtained by the controller 20 of the chargedparticle beam system 1, for example, by data transfer from anotherdevice, by data transfer via a network such as the internet, by readingfrom a data storage and the like. For this purpose, the charged particlebeam system 1 can comprise a data interface for receiving the coordinatedata and a data storage for storing the coordinate data, respectively.

The coordinates of the ROIs 61, 62 can be determined in the first placeby any kind of method or instrument. For example, the coordinates of theROIs 61, 62 can be obtained by light microscopy, dark field microscopy,charged particle beam microscopy, atomic force microcopy and the like.In particular, the coordinates of the ROIs 61, 62 can be obtained usingthe charged particle beam system 1. Further, the coordinates of the ROIs61, 62 can be determined using design information of the sample 3 andthe ROIs 61, 62. For example, in a preparation process, the sample 3including the ROIs 61, 62 can be generated based on the designinformation. The design information can comprise information about therelative positions of the ROIs 61, 62, distances between the ROIs 61, 62and the like. Still further, for example in chip production, the ROIs61, 62 are located on a wafer (i.e. sample 3), and the wafer is preparedand transported by an automated system. Consequently, the orientationand location of the wafer is generally stored in a controller of theautomated system, and the locations of the ROIs 61, 62 on the wafer aregenerally stored in design information. Therefore, the coordinates ofthe ROIs can be provided by the controller of the automated system.

In steps S2 and S3, the first DAC circuit 41 and the second DAC circuit42 of the deflection subsystem 40 are configured based on the obtainedcoordinates of the ROIs 61, 62. In particular, in step S2, the firstamplification of the first amplifier 46 is configured; and in step S3,the second amplification of the second amplifier 48 is configured. Thecontroller 20 can be configured to determine distances between the ROIs61, 62 and sizes, shapes and the like of the ROIs 61, 62 which are usedfor the configuring of the first DAC circuit 41 and the second DACcircuit 42. In particular, controller 20 can be configured to determinea setting of the first DAC circuit 41 (first amplification of the firstamplifier 46) and a setting of the second DAC circuit 42 (secondamplification of the second amplifier 48) based on obtained coordinatesof the ROIs 61, 62 so that a predefined set of constraints is fulfilled.

For example, in accordance with the illustration of FIG. 4 , the firstDAC circuit 41, in particular the first amplification of the firstamplifier 46, can be set (i.e., selected) so that the first scanningrange SR1 is at least as large as the largest of the ROIs 61, 62.Consequently, each of the ROIs 61, 62 is scannable at high precision andhigh resolution, i.e. by varying the first digital deflection signal(40D1) while maintaining the second digital deflection signal (40D2).Further, the second DAC circuit 42, in particular the secondamplification of the second amplifier 48, can be set (i.e., selected) sothat the second scanning range SR2 is at least as large as the largestdistance between the ROIs 61, 62. Consequently, all ROIs 61, 62 can bescanned without moving the stage 4. I.e., images of the ROIs 61, 62 canbe recorded while maintaining the stage 4 in position.

Subsequently, in step S4, images of the ROIs 61, 62 are recorded usingthe configurations made. In particular, the charged particle beam 2 canbe scanned over the ROIs 61, 62 and interaction products (e.g.,backscattered or secondary electrons, backscattered or secondary ions,radiation, etc.) of the charged particle beam 2 with the sample 3 aredetected in order to record the images. Using the configurations madeabove, an image of each of the ROIs 61, 62 can be recorded by scanningthe charged particle beam 2 over the respective ROI by varying the firstdigital deflection signal 40D1 and maintaining the second digitaldeflection signal 40D2. For example, referring to FIG. 4 , an image ofthe ROI 61 can be recorded by varying the first digital deflectionsignal 40D1 from 0 to n−1 and maintaining the second digital deflectionsignal 40D2 at 0. For recording an image of the ROI 62, the seconddigital deflection signal 40D2 is varied to m−1 and maintained at m−1while scanning the charged particle beam 2 over the ROI 62 by varyingthe first digital deflection signal 40D1.

Referring back to FIG. 2 , the deflection subsystem 50 of the deflectionsystem 13 is structured in the same manner as the deflection subsystem40. However, the deflection subsystem 50 is provided to deflect thecharged particle beam 2 in another deflection direction different fromthe deflection direction along which the charged particle beam 2 can bedeflected by the deflection subsystem 40. Therefore, the deflectionsystem 13 can be configured to deflect the charged particle beam 2 intomultiple different deflection directions.

Despite having the same structure as the deflection system 40, thedeflection subsystem 50 and its components can be configured and setindependently from the deflection subsystem 40. The deflection subsystem50 comprises a first DAC circuit 51 similar to the first DAC circuit 41,a second DAC circuit 52 similar to the second DAC circuit 42, a summer53 similar to the summer 43, and a field generator 54 similar to thefield generator 44. A more detailed description of the deflectionsubsystem 50 is omitted for brevity; reference is made to thecorresponding deflection subsystem 40 and its components.

With reference to FIGS. 6 to 9 , exemplary embodiments of a methodaccording to the third aspect of the invention are described. The methodcomprises recording a plurality of images representing a plurality ofdifferent regions of interest (ROIs) A, B, C on a sample 3. FIG. 6illustrates an example of the ROIs A, B, C on the sample 3.

The recording of the plurality of images of the ROIs A, B, C comprisesscanning a charged particle beam 2 over a plurality of scan regions sothat a set of predetermined constraints is fulfilled. FIG. 6 illustratesan example of the scan regions A1 to A4, B1 to B4, C1 to C4 on thesample 3 and a scan order of scanning the scan regions A1 to A4, B1 toB4, C1 to C4.

The scanning of the charged particle beam 2 over each of the scanregions A1 to A4, B1 to B4, C1 to C4 comprises directing the chargedparticle beam 2 to a plurality of different locations of the respectivescan region; detecting, during the scanning of the charged particle beamover the respective scan region, interaction products of the chargedparticle beam 2 with the sample 3; and storing measurement data based ona detection rate of the detecting. Accordingly, a scan region is aregion of the sample to which the charged particle beam 2 is directedfor recording a portion of an image of a region of interest comprisingthe scan region.

The constraints comprise that each of the ROIs comprises a plurality ofthe scan regions. In the example illustrated in FIG. 6 , the ROI Acomprises four scan regions A1, A2, A3 and A4; the ROI B comprises fourscan regions B1, B2, B3 and B4; and the ROI C comprises four scanregions C1, C2, C3 and C4. In general the number of scan regions per ROIcan be different for each of the ROIs. In practice, the number of scanregions per ROI will be much greater than four. For example, each of theregions of interest can comprise at least 10 or at least 100 scanregions. That is, the number of scan regions per ROI can amount to atleast 10 or at least 100.

For example, as illustrated in FIG. 6 , the scan regions A1 to A4, B1 toB4, C1 to C4 can be line segments of the ROIs. However, any portion of aROI can be selected as a scan region. A maximum distance betweenadjacent scan regions belonging to a same one of the regions of interestshould amount to at most 200 nm or at most 100 nm or at most 50 nm or atmost 20 nm or at most 10 nm. Otherwise, the image has poor resolution.

The constraints further comprise that each two scan regions to bescanned in succession are separated by at least a first minimum distanceamounting to at least 100 nm. The expression “in succession” meansdirectly one after the other in time without interruption by scanning ofany other scan region. In other words, two scan regions to be scanned insuccession are a scan region to be scanned and a scan region to bescanned directly thereafter (next). In FIG. 6 , the order of thescanning of the scan regions A1 to A4, B1 to B4, C1 to C4 is illustratedby arrows connecting the scan regions A1 to A4, B1 to B4, C1 to C4. Inparticular, the order of the scanning of the scan regions A1 to A4, B1to B4, C1 to C4 illustrated in the example of FIG. 6 is: A1, B1, C1, A2,B2, C2, A3, B3, C3, A4, B4, C4. All two scan regions to be scanned insuccession are (A1, B1), (B1, C1), (C1, A2), (A2, B2), (B2, C2), (C2,A3), (A3, B3), (B3, C3), (C3, A4), (A4, B4), (B4, C4).

According to the constraint, each two scan regions to be scanned insuccession are separated by at least the first minimum distance. Inparticular, this means each two scan regions to be scanned in successionare separated by a shortest distance to each other which amounts to atleast the first minimum distance. As an illustrative example, FIG. 7illustrates the shortest distances between the first few two scanregions to be scanned in succession: d1 denotes the shortest distancebetween the first two scan regions to be scanned in succession (A1, B1);d2 denotes the shortest distance between the second two scan regions tobe scanned in succession (B1, C1); and d3 denotes the shortest distancebetween the third two scan regions to be scanned in succession (C1, A2).As the distance between each two scan regions to be scanned insuccession is fairly large, charge accumulated at a scan region haslittle effect on the scanning of the charged particle beam over the scanregion to be scanned next.

This effect can be improved by increasing the first minimum distance.For example, the first minimum distance can amount to at least 200 nm orat least 500 nm or at least 1000 nm.

The constraints further comprise that each two scan regions to bescanned in succession belong to different ones of the regions ofinterest. In the example illustrated in FIG. 6 , the order of the ROIsassociated with the order of the scanning of the scan regions is: A, B,C, A, B, C, A, B, C, A, B, C.

FIG. 8 illustrates further details about the regions of interest. TheROIs A, B, C are not overlapping each other. That is, boundaries of theROIs A, B, C illustrated as solid lines do not intersect each other. Inparticular, the ROIs can be separated by at least 10 nm or at least 50nm or at least 100 nm or at least 500 nm or at least 1000 nm. That is, ashortest distance between adjacent ROIs can amount to at least 10 nm orat least 50 nm or at least 100 nm or at least 500 nm or at least 1000nm. In FIG. 8 , the shortest distance between the ROI A and the ROI B isdenoted dAB; the shortest distance between the ROI B and the ROI C isdenoted dBC; and the shortest distance between the ROI A and the ROI Cis denoted dAC.

Further or alternatively, the ROIs can be separated by at least half ofa size of a smallest one of the ROIs. That is, a shortest distancebetween boundaries of adjacent ROIs amounts to at least half of the sizeof the smallest one of the ROIs. The size of a ROI can be an averagediameter of the ROI, for example.

The method has the effect that a plurality of images with reducedinterference due to charge accumulation in the sample can be recordedusing a charged particle beam. While the above example refers to threeimages and three ROIs A, B, C only, the method can be performed for twoor more than three images and ROIs, respectively. While the aboveexample refers to four scan regions per ROI only, the method can beperformed using any number of at least two for the number of scanregions per ROI.

The recorded images can be displayed, for example, by the output device33.

FIG. 9 is a flowchart illustrating another embodiment of the methodaccording to the third aspect of the invention using the chargedparticle beam system 1 illustrated in FIG. 1 configured according to themethod according to the second aspect of the present invention.

In step S11, coordinates of regions of interest A, B, C are obtained.This step corresponds to step S1 of the method illustrated in FIG. 5 ,the description of which is referred to.

Subsequent to step S11, in step S12, scan regions A1 to A4, B1 to B4, C1to C4 and a scan order are determined based on the coordinates of theROIs A, B, C obtained in step S11. The scan order defines an order ofthe scanning of the scan regions. The scan regions A1 to A4, B1 to B4,C1 to C4 and the scan order are determined so that the predeterminedconstraints are fulfilled. As described with reference to FIGS. 6 to 8 ,the constraints comprise: each of the ROIs A, B, C comprises a pluralityof the scan regions A1 to A4, B1 to B4, C1 to C4; each two scan regionsto be scanned in succession are separated by at least a first minimumdistance amounting to at least 100 nm; and each two scan regions to bescanned in succession belong to different ones of the ROIs A, B, C.

Based on the coordinates of the ROIs A, B, C, the controller 20 of thecharged particle beam system 1 or any other processor can be used todetermine the scan regions and the scan order. The scan regions and thescan order can be determined prior to the scanning of the scan regions.Alternatively, the scan regions and the scan order can be determined inparallel to the scanning of the scan regions as required. A multiplicityof methods, algorithm and devices can be used to determine the scanregions and the scan order. However, for the method at hand, theparticular implementation of the determining of the scan regions and thescan order is not relevant as long as the predefined constraints arefulfilled.

Subsequent to step S12, in step S13, a scan region to be scanned next isselected among the scan regions A1 to A4, B1 to B4, C1 to C4 inaccordance with the scan order. The selecting of the scan regioncomprises varying the second digital deflection signal 40D2. Theselecting of the scan region can further comprise varying the seconddigital deflection signal 50D2 of the deflection subsystem 50.

Subsequent to step S13, in step S14, the charged particle beam 2 isscanned over the selected scan region. The scanning of the chargedparticle beam 2 over the selected scan region comprises converting thefirst digital deflection signal 40D1 into the first analog output signal40A1; converting the second digital deflection signal 40D2 into thesecond analog output signal 40A2; generating the analog deflectionsignal 40A based on the sum of the first analog output signal 40A1 andthe second analog output signal 40A2; deflecting the charged particlebeam 2 using the analog deflection signal 40A; and varying the firstdigital deflection signal 40D1 while maintaining the second digitaldeflection signal 40D2.

The scanning of the charged particle beam 2 over the selected scanregion can further comprise converting the first digital deflectionsignal 50D1 into the first analog output signal 50A1; converting thesecond digital deflection signal 50D2 into the second analog outputsignal 50A2; generating the analog deflection signal 50A based on thesum of the first analog output signal 50A1 and the second analog outputsignal 50A2; deflecting the charged particle beam 2 using the analogdeflection signal 50A; and varying the first digital deflection signal50D1 while maintaining the second digital deflection signal 50D2.

Subsequent to step S14, in step S15, it is determined whether all of thescan regions A1 to A4, B1 to B4, C1 to C4 were scanned. If all of thescan regions A1 to A4, B1 to B4, C1 to C4 were scanned, the images ofthe regions of interest A, B, C are fully recorded and the method ends.If not all of the scan regions A1 to A4, B1 to B4, C1 to C4 werescanned, steps S13 to S15 are repeated, whereby another one of the scanregions A1 to A4, B1 to B4, C1 to C4 is scanned. Steps S13 to S15 arerepeated until all of the scan regions A1 to A4, B1 to B4, C1 to C4 werescanned, that is, until all of the images of the s of interest A, B, Care fully recorded.

In some implementations, the processing unit 32 and the controller 20can each include one or more data processors for processing data, one ormore storage devices for storing data, and/or one or more computerprograms including instructions that when executed by the processingunit 32 or the controller 20 cause the processing unit 32 or thecontroller 20 to carry out the processes described above.

In some implementations, the processing unit 32 and the controller 20can each include digital electronic circuitry, computer hardware,firmware, software, or any combination of the above. The featuresrelated to processing of data can be implemented in a computer programproduct tangibly embodied in an information carrier, e.g., in amachine-readable storage device, for execution by a programmableprocessor; and method steps can be performed by a programmable processorexecuting a program of instructions to perform functions of thedescribed implementations by operating on input data and generatingoutput. Alternatively or addition, the program instructions can beencoded on a propagated signal that is an artificially generated signal,e.g., a machine-generated electrical, optical, or electromagneticsignal, that is generated to encode information for transmission tosuitable receiver apparatus for execution by a programmable processor.

In some implementations, the operations associated with processing ofdata described in this document can be performed by one or moreprogrammable processors executing one or more computer programs toperform the functions described in this document. A computer program canbe written in any form of programming language, including compiled orinterpreted languages, and it can be deployed in any form, including asa stand-alone program or as a module, component, subroutine, or otherunit suitable for use in a computing environment.

For example, the processing unit 32 and the controller 20 can each beconfigured to be suitable for the execution of a computer program andcan include, by way of example, both general and special purposemicroprocessors, and any one or more processors of any kind of digitalcomputer. Generally, a processor will receive instructions and data froma read-only storage area or a random access storage area or both.Elements of a computer include one or more processors for executinginstructions and one or more storage area devices for storinginstructions and data. Generally, a computer will also include, or beoperatively coupled to receive data from, or transfer data to, or both,one or more machine-readable storage media, such as hard drives,magnetic disks, magneto-optical disks, or optical disks.Machine-readable storage media suitable for embodying computer programinstructions and data include various forms of non-volatile storagearea, including by way of example, semiconductor storage devices, e.g.,EPROM, EEPROM, and flash storage devices; magnetic disks, e.g., internalhard disks or removable disks; magneto-optical disks; and CD-ROM andDVD-ROM discs.

In some implementations, the processes for operating the chargedparticle beam system described above can be implemented using softwarefor execution on one or more mobile computing devices, one or more localcomputing devices, and/or one or more remote computing devices. Forinstance, the software forms procedures in one or more computer programsthat execute on one or more programmed or programmable computer systems,either in the mobile computing devices, local computing devices, orremote computing systems (which may be of various architectures such asdistributed, client/server, or grid), each including at least oneprocessor, at least one data storage system (including volatile andnon-volatile memory and/or storage elements), at least one wired orwireless input device or port, and at least one wired or wireless outputdevice or port.

In some implementations, the software may be provided on a medium, suchas a CD-ROM, DVD-ROM, or Blu-ray disc, readable by a general or specialpurpose programmable computer or delivered (encoded in a propagatedsignal) over a network to the computer where it is executed. Thefunctions may be performed on a special purpose computer, or usingspecial-purpose hardware, such as coprocessors. The software may beimplemented in a distributed manner in which different parts of thecomputation specified by the software are performed by differentcomputers. Each such computer program is preferably stored on ordownloaded to a storage media or device (e.g., solid state memory ormedia, or magnetic or optical media) readable by a general or specialpurpose programmable computer, for configuring and operating thecomputer when the storage media or device is read by the computer systemto perform the procedures described herein. The inventive system mayalso be considered to be implemented as a computer-readable storagemedium, configured with a computer program, where the storage medium soconfigured causes a computer system to operate in a specific andpredefined manner to perform the functions described herein.

While this specification contains many specific implementation details,these should not be construed as limitations on the scope of anyinventions or of what may be claimed, but rather as descriptions offeatures specific to particular embodiments of particular inventions.Numerous variations and alternative embodiments will be apparent to aperson skilled in the art, for example through combination and/orexchange of features of individual embodiments. Accordingly, suchvariations and alternative embodiments are concomitantly encompassed bythe present invention, and the scope of the invention is restricted onlywithin the meaning of the appended claims and the equivalents thereof.

Certain features that are described in this specification in the contextof separate embodiments can also be implemented in combination in asingle embodiment. Conversely, various features that are described inthe context of a single embodiment can also be implemented in multipleembodiments separately or in any suitable subcombination.

Similarly, while operations are depicted in the drawings in a particularorder, this should not be understood as requiring that such operationsbe performed in the particular order shown or in sequential order, orthat all illustrated operations be performed, to achieve desirableresults. Moreover, the separation of various system components in theembodiments described above should not be understood as requiring suchseparation in all embodiments.

Although the present invention is defined in the attached claims, itshould be understood that the present invention can also be defined inaccordance with the following embodiments:

Embodiment 1: A charged particle beam system (1), comprising:

a charged particle beam source (11) configured to generate a chargedparticle beam (2);

an objective lens (12) configured to focus the charged particle beam (2)into a focal plane (6);

a deflection system (13) configured to deflect the charged particle beam(2), wherein the deflection system (13) comprises at least onedeflection subsystem (40, 50), wherein each deflection subsystem (40,50) comprises:

a first DAC circuit (41) configured to convert a first digitaldeflection signal (40D1) into a first analog output signal (40A1) withina first operating range (OR1) at steps of a first step height (SH1),

a second DAC circuit (42) configured to convert a second digitaldeflection signal (40D2) into a second analog output signal (40A2)within a second operating range (OR2) at steps of a second step height(SH2),

a summer (43) configured to receive the first analog output signal(40A1) and the second analog output signal (40A2) and to output ananalog deflection signal (40A) based on the sum of the received firstanalog output signal (40A1) and the received second analog output signal(40A2), and

a field generator (44) configured to receive the analog deflectionsignal (40A) and to generate a magnetic and/or electric field fordeflecting the charged particle beam (2) using the received analogdeflection signal (40A);

wherein the charged particle beam system (1) further comprises:

-   -   a controller (20) configured to generate the first digital        deflection signal (40D1) and the second digital deflection        signal (40D2) separately for each deflection subsystem (40, 50).

Embodiment 2: The charged particle beam system (1) according toembodiment 1,

wherein the first operating range (OR1) is approximately equal to thesecond step height (SH2).

Embodiment 3: The charged particle beam system (1) according toembodiment 1 or 2,

wherein a ratio of the second operating range (OR2) to the firstoperating range (OR1) amounts to at least 10, in particular at least100, more in particular at least 200.

Embodiment 4: The charged particle beam system (1) according to any oneof embodiments 1 to 3,

wherein an accuracy of converting the first digital deflection signal(40D1) into the first analog output signal (40A1) achieved by the firstDAC circuit (41) is greater than an accuracy of converting the seconddigital deflection signal (40D2) into the second analog output signal(40A2) achieved by the second DAC circuit (42).

Embodiment 5: The charged particle beam system (1) according to any oneof embodiments 1 to 4,

wherein the first DAC circuit (41) comprises a first DAC (45) configuredto convert the first digital deflection signal (40D1) into a firstanalog intermediate signal (40I1) and a first amplifier (46) configuredto generate the first analog output signal (40A1) by amplifying thefirst analog intermediate signal (40I1) with a first amplification;

wherein the second DAC circuit (42) comprises a second DAC (47)configured to convert the second digital deflection signal (40D2) into asecond analog intermediate signal (40I2) and a second amplifier (48)configured to generate the second analog output signal (40A2) byamplifying the second analog intermediate signal (40I2) with a secondamplification.

Embodiment 6. The charged particle beam system (1) according toembodiment 5,

wherein the first amplification defines the first step height (SH1),

wherein the second amplification defines the second step height (SH2),

wherein a bit depth of the first DAC (45) and the first amplificationdefine the first operating range (OR1),

wherein a bit depth of the second DAC (47) and the second amplificationdefine the second operating range (OR2).

Embodiment 7: The charged particle beam system (1) according toembodiment 5 or 6,

wherein the first amplification and the second amplification areselected so that the first operating range (OR1) is approximately equalto the second step height (SH2).

Embodiment 8: The charged particle beam system (1) according to any oneof embodiments 5 to 7,

wherein the first amplification and the second amplification areselected so that a ratio of the second operating range (OR2) to thefirst operating range (OR1) amounts to at least 10, in particular atleast 100, more in particular at least 200.

Embodiment 9: The charged particle beam system (1) according to any oneof embodiments 5 to 8,

wherein an accuracy of converting the first digital deflection signal(40D1) into the first analog intermediate signal (40I1) achieved by thefirst DAC (45) is greater than an accuracy of converting the seconddigital deflection signal (40D2) into the second analog intermediatesignal (40I2) achieved by the second DAC (47).

Embodiment 10: The charged particle beam system (1) according to any oneof embodiments 5 to 9,

wherein a bit depth of the first DAC (45) is greater than a bit depth ofthe second DAC (47).

Embodiment 11: The charged particle beam system (1) according to any oneof embodiments 1 to 10,

wherein the deflection system (13) is configured to deflect the chargedparticle beam (2) so that the charged particle beam (2) can be directedto a plurality of different locations in the focal plane (6).

Embodiment 12: A method of operating the charged particle beam system(1) according to any one of embodiments 1 to 11, the method comprising:

obtaining coordinates of a plurality of regions of interest (61, 62) ona sample (3);

configuring the first DAC circuit (41) so that a first scanning range(SR1) provided by the first DAC circuit (41) is at least as large as thelargest of the regions of interest (61, 62), the first scanning range(SR1) representing a length of a region in the focal plane (6) of theobjective lens (12) scannable by varying the first digital deflectionsignal (40D1) while maintaining the second digital deflection signal(40D2);

configuring the second DAC circuit (42) so that a second scanning range(SR2) provided by the second DAC circuit (42) is at least as large asthe largest distance (d) between the regions of interest (61, 62), thesecond scanning range (SR2) representing a length of a region in thefocal plane (6) of the objective lens (12) scannable by varying thesecond digital deflection signal (40D2) while maintaining the firstdigital deflection signal (40D1); and

recording images of the regions of interest (61, 62) using theconfigurations made.

Embodiment 13: The method according to embodiment 12, wherein therecording of each of the images comprises:

scanning the charged particle beam (2) over the region of interestassociated with the respective image by varying the first digitaldeflection signal (40D1) and maintaining the second digital deflectionsignal (40D2), and

detecting an interaction product of the charged particle beam (2) withthe sample (3) during the scanning.

Embodiment 14: The method according to embodiment 12 or 13, wherein therecording of the images further comprises:

selecting a next one of the regions of interest by varying the seconddigital deflection signal (40D2).

Embodiment 15: The method according to any one of embodiments 12 to 14,wherein the recording of the images further comprises:

maintaining a stage (4) in position, the stage (4) holding the sample(3).

Embodiment 16: The method according to any one of embodiments 12 to 15of operating the charged particle beam system (1) according to any oneof embodiments 5 to 10, wherein the configuring of the first DAC circuit(41) comprises setting the first amplification; and the configuring ofthe second DAC (42) circuit comprises setting the second amplification.

Embodiment 17: A computer program comprising instructions which, whenexecuted by a controller of a charged particle beam system (1) accordingto any one of embodiments 1 to 11, enable the charged particle beamsystem (1) to execute the method according to any one of embodiments 12to 16.

Embodiment 18: A method of recording a plurality of images representingdifferent regions of interest of a sample, the method comprising:

recording a plurality of images representing a plurality of differentregions of interest (A, B, C) on a sample (3), comprising:

scanning a charged particle beam (2) over a plurality of scan regions(A1 to A4, B1 to B4, C1 to C4),

wherein each of the regions of interest (A, B; C) comprises a pluralityof the scan regions (A1 to A4, B1 to B4, C1 to C4),

wherein each two scan regions to be scanned in succession are separatedby at least a first minimum distance amounting to at least 100 nm, and

wherein each two scan regions to be scanned in succession belong todifferent ones of the regions of interest (A, B, C).

Embodiment 19: The method according to embodiment 18, furthercomprising:

determining the plurality of scan regions (A1 to A4, B1 to B4, C1 to C4)and a scan order based on coordinates of the plurality of regions ofinterest (A, B, C),

wherein the scan order defines an order of the scanning of the scanregions (A1 to A4, B1 to B4, C1 to C4).

Embodiment 20: The method according to embodiment 18 or 19, wherein thescanning of the charged particle beam (2) over each of the scan regions(A1 to A4, B1 to B4, C1 to C4) comprises:

converting a first digital deflection signal (40D1) into a first analogoutput signal (40A1);

converting a second digital deflection signal (40D2) into a secondanalog output signal (40A2);

generating an analog deflection signal (40A) based on the sum of thefirst analog output signal (40A1) and the second analog output signal(40A2); and

deflecting the charged particle beam (2) using the analog deflectionsignal (40A).

Embodiment 21: The method according to embodiment 20, wherein thescanning of the charged particle beam (2) over each of the scan regions(A1 to A4, B1 to B4, C1 to C4) further comprises:

varying the first digital deflection signal (40D1) while maintaining thesecond digital deflection signal (40D2).

Embodiment 22: The method according to embodiment 20 or 21, wherein therecording of the plurality of images further comprises:

selecting, among the scan regions (A1 to A4, B1 to B4, C1 to C4), thescan region to be scanned next by varying the second digital deflectionsignal (40D2).

Embodiment 23: The method according any one of embodiments to 18 to 22,wherein the first minimum distance amounts at least 200 nm or at least500 nm or at least 1000 nm.

Embodiment 24: The method according to any one of embodiments 18 to 23,wherein the scan regions (A1 to A4, B1 to B4, C1 to C4) are linesegments of the regions of interest (A, B, C).

Embodiment 25: The method according to any one of embodiments 18 to 24,wherein a maximum distance between adjacent scan regions belonging to asame one of the regions of interest (A, B, C) amounts to at most 200 nmor at most 100 nm or at most 50 nm or at most 20 nm or at most 10 nm.

Embodiment 26: The method according to any one of embodiments 18 to 25,wherein the regions of interest (A, B, C) are not overlapping eachother.

Embodiment 27: The method according to any one of embodiments 18 to 26,wherein the regions of interest (A, B, C) are separated by at least 10nm or at least 50 nm or at least 100 nm or at least 500 nm or at least1000 nm.

Embodiment 28: The method according to any one of embodiments 18 to 27,wherein the regions of interest (A, B, C) are separated by at least halfof a size of a smallest one of the regions of interest (A, B, C).

Embodiment 29: The method according to any one of embodiments 18 to 28,wherein the recording of the plurality of images further comprises:

detecting, during the scanning of the charged particle beam (2) over thescan regions (A1 to A4, B1 to B4, C1 to C4), interaction products of thecharged particle beam (2) with the sample (3); and

storing measurement data based on a detection rate of the detecting ofthe interaction products of the charged particle beam (2) with thesample (3).

Embodiment 30: The method according to any one of embodiments 18 to 29,wherein each of the regions of interest (A, B, C) comprises at least 10or at least 100 of the scan regions (A1 to A4, B1 to B4, C1 to C4).

Embodiment 31: The method according to any one of embodiments 18 to 30,further comprising:

displaying the images.

Embodiment 32: The method according to any one of embodiments 18 to 31,wherein the method is performed using the charged particle beam system(1) according to any one of embodiments 1 to 11.

Embodiment 33: A computer program comprising instructions which, whenexecuted by a controller of a charged particle beam system, inparticular the controller (20) of the charged particle beam system (1)according to any one of embodiments 1 to 11, enable the charged particlebeam system to execute the method according to any one of embodiments 18to 32.

What is claimed is:
 1. A charged particle beam system, comprising: acharged particle beam source configured to generate a charged particlebeam; an objective lens configured to focus the charged particle beaminto a focal plane; a deflection system configured to deflect thecharged particle beam, wherein the deflection system comprises at leastone deflection subsystem, wherein each deflection subsystem comprises: afirst DAC circuit configured to convert a first digital deflectionsignal into a first analog output signal within a first operating range(OR1) at steps of a first step height (SH1), a second DAC circuitconfigured to convert a second digital deflection signal into a secondanalog output signal within a second operating range (OR2) at steps of asecond step height (SH2), a summer configured to receive the firstanalog output signal and the second analog output signal and to outputan analog deflection signal based on the sum of the received firstanalog output signal and the received second analog output signal, and afield generator configured to receive the analog deflection signal andto generate a magnetic and/or electric field for deflecting the chargedparticle beam using the received analog deflection signal; wherein thecharged particle beam system further comprises: a controller configuredto generate the first digital deflection signal and the second digitaldeflection signal separately for each deflection subsystem.
 2. Thecharged particle beam system of claim 1, wherein the first operatingrange (OR1) is approximately equal to the second step height (SH2). 3.The charged particle beam system of claim 1, wherein a ratio of thesecond operating range (OR2) to the first operating range (OR1) amountsto at least 10, in particular at least 100, more in particular at least200.
 4. The charged particle beam system of claim 1, wherein an accuracyof converting the first digital deflection signal into the first analogoutput signal achieved by the first DAC circuit is greater than anaccuracy of converting the second digital deflection signal into thesecond analog output signal achieved by the second DAC circuit.
 5. Thecharged particle beam system of claim 1, wherein the first DAC circuitcomprises a first DAC configured to convert the first digital deflectionsignal into a first analog intermediate signal and a first amplifierconfigured to generate the first analog output signal by amplifying thefirst analog intermediate signal with a first amplification; wherein thesecond DAC circuit comprises a second DAC configured to convert thesecond digital deflection signal into a second analog intermediatesignal and a second amplifier configured to generate the second analogoutput signal by amplifying the second analog intermediate signal with asecond amplification.
 6. The charged particle beam system of claim 5,wherein the first amplification defines the first step height (SH1),wherein the second amplification defines the second step height (SH2),wherein a bit depth of the first DAC and the first amplification definethe first operating range (OR1), wherein a bit depth of the second DACand the second amplification define the second operating range (OR2). 7.The charged particle beam system of claim 5, wherein the firstamplification and the second amplification are selected so that thefirst operating range (OR1) is approximately equal to the second stepheight (SH2).
 8. The charged particle beam system of claim 5, whereinthe first amplification and the second amplification are selected sothat a ratio of the second operating range (OR2) to the first operatingrange (OR1) amounts to at least 10, in particular at least 100, more inparticular at least
 200. 9. The charged particle beam system of claim 5,wherein an accuracy of converting the first digital deflection signalinto the first analog intermediate signal achieved by the first DAC isgreater than an accuracy of converting the second digital deflectionsignal into the second analog intermediate signal achieved by the secondDAC.
 10. The charged particle beam system of claim 5, wherein a bitdepth of the first DAC is greater than a bit depth of the second DAC.11. The charged particle beam system of claim 1, wherein the deflectionsystem is configured to deflect the charged particle beam so that thecharged particle beam can be directed to a plurality of differentlocations in the focal plane.
 12. A method of operating the chargedparticle beam system of claim 1, the method comprising: obtainingcoordinates of a plurality of regions of interest on a sample;configuring the first DAC circuit so that a first scanning range (SR1)provided by the first DAC circuit is at least as large as the largest ofthe regions of interest, the first scanning range (SR1) representing alength of a region in the focal plane of the objective lens scannable byvarying the first digital deflection signal while maintaining the seconddigital deflection signal; configuring the second DAC circuit so that asecond scanning range (SR2) provided by the second DAC circuit is atleast as large as the largest distance (d) between the regions ofinterest, the second scanning range (SR2) representing a length of aregion in the focal plane of the objective lens scannable by varying thesecond digital deflection signal while maintaining the first digitaldeflection signal; and recording images of the regions of interest usingthe configurations made.
 13. The method of claim 12, wherein therecording of each of the images comprises: scanning the charged particlebeam over the region of interest associated with the respective image byvarying the first digital deflection signal and maintaining the seconddigital deflection signal, and detecting an interaction product of thecharged particle beam with the sample during the scanning.
 14. Themethod of claim 12, wherein the recording of the images furthercomprises: selecting a next one of the regions of interest by varyingthe second digital deflection signal.
 15. The method of claim 12,wherein the recording of the images further comprises: maintaining astage in position, the stage holding the sample.
 16. The method of claim12 of operating the charged particle beam system of claim 5, wherein theconfiguring of the first DAC circuit comprises setting the firstamplification; and the configuring of the second DAC circuit comprisessetting the second amplification.
 17. A computer program comprisinginstructions which, when executed by a controller of a charged particlebeam system of claim 1, enable the charged particle beam system toexecute the method of claim
 12. 18. A method of recording a plurality ofimages representing different regions of interest of a sample, themethod comprising: recording a plurality of images representing aplurality of different regions of interest on a sample, comprising:scanning a charged particle beam over a plurality of scan regions,wherein each of the regions of interest comprises a plurality of thescan regions, wherein each two scan regions to be scanned in successionare separated by at least a first minimum distance amounting to at least100 nm, and wherein each two scan regions to be scanned in successionbelong to different ones of the regions of interest.
 19. The method ofclaim 18, further comprising: determining the plurality of scan regionsand a scan order based on coordinates of the plurality of regions ofinterest, wherein the scan order defines an order of the scanning of thescan regions.
 20. The method of claim 18, wherein the scanning of thecharged particle beam over each of the scan regions comprises:converting a first digital deflection signal into a first analog outputsignal; converting a second digital deflection signal into a secondanalog output signal; generating an analog deflection signal based onthe sum of the first analog output signal and the second analog outputsignal; and deflecting the charged particle beam using the analogdeflection signal.
 21. The method of claim 20, wherein the scanning ofthe charged particle beam over each of the scan regions furthercomprises: varying the first digital deflection signal while maintainingthe second digital deflection signal.
 22. The method of claim 20,wherein the recording of the plurality of images further comprises:selecting, among the scan regions, the scan region to be scanned next byvarying the second digital deflection signal.
 23. The method of claim18, wherein the first minimum distance amounts at least 200 nm or atleast 500 nm or at least 1000 nm.
 24. The method of claim 18, whereinthe scan regions are line segments of the regions of interest.
 25. Themethod of claim 18, wherein a maximum distance between adjacent scanregions belonging to a same one of the regions of interest amounts to atmost 200 nm or at most 100 nm or at most 50 nm or at most 20 nm or atmost 10 nm.
 26. The method of claim 18, wherein the regions of interestare not overlapping each other.
 27. The method of claim 18, wherein theregions of interest are separated by at least 10 nm or at least 50 nm orat least 100 nm or at least 500 nm or at least 1000 nm.
 28. The methodof claim 18, wherein the regions of interest are separated by at leasthalf of a size of a smallest one of the regions of interest.
 29. Themethod of claim 18, wherein the recording of the plurality of imagesfurther comprises: detecting, during the scanning of the chargedparticle beam over the scan regions, interaction products of the chargedparticle beam with the sample; and storing measurement data based on adetection rate of the detecting of the interaction products of thecharged particle beam with the sample.
 30. The method of claim 18,wherein each of the regions of interest comprises at least 10 or atleast 100 of the scan regions.
 31. The method of claim 18, furthercomprising: displaying the images.
 32. The method of claim 18, whereinthe method is performed using the charged particle beam system ofclaim
 1. 33. A computer program comprising instructions which, whenexecuted by a controller of a charged particle beam system, inparticular the controller of the charged particle beam system of claim1, enable the charged particle beam system to execute the method ofclaim 18.